WHAT IS PLA
PLA or Polylactic acid is a thermoplastic polyester. It is commonly derived from renewable resources, such as corn starch, tapioca roots or sugarcane. One of the most attractive things about PLA is that it naturally degrades when exposed to the environment. For example, an item made of PLA in the ocean has a degradation time on the order of six months to two years. Compare this to conventional plastics, which take from 500 to 1,000 years to degrade. It is important to point out that although PLA will degrade in an exposed natural environment it is very robust when used in any normal application such as a printed toy or a critical piece of a printer. .
PLA is used in many industries from food packaging to biodegradable medical implants such as sutures, tissue screws, and tacks.
If you have printed with ABS, you will find PLA to be harder, wear more slowly, and be easier to get a nice flat part with. PLA is less thermally contractive and much easier to print big parts with. The thing to consider is that being stiffer and harder also means that it is more brittle. If the part you're printing will be used where it might receive a lot of banging or sharp collisions, PLA may not be the best material.
The other important consideration when printing parts in PLA is knowing what sorts of temperatures they will be subjected to. PLA becomes soft at 60c and will deform if used in environments that remain above those temperatures for any prolonged time. If you have been printing a lot of ABS, you'll need to drop your nozzle/platform height by about 0.4 - 0.6mm, with PLA you want the material to kind of dribble onto the bed, rather that be squished out completely flat.
GETTING THE FIRST LAYER RIGHT
The first layer is the most important part of any print. There are a few things you need to do to get the first layer to stick well.
- You need the print bed to be level.
- You need the extruder to be homed to the correct height from the bed. If you've been printing with ABS, then drop the nozzle height by about 0.4mm
- You need a good base material for your PLA to adhere to. E.g. Buildtak, glass or 3M blue tape.
- Always print a small part to test the correct layer height. Too close and you'll hear the extruder clicking (slipping on the filament).
3M Blue Tape Painters Tape or BuildTak (or preferred option) are the easiest and fastest ways to get a great print from PLA. Here is a quick checklist of things you want to make sure you are doing.
- Check that the Blue Tape creates an even layer. Don't miss any spots. Don't overlap the edges.
- Don't pre-heat the bed when using Blue Tape, just click print from a cold bed
- Replace any tape strips that get damage when removing parts.
- Replace the tape after 5-10 prints or when parts stop sticking.
- If your first layer is not sticking - make sure the print head is close enough.
Blue Tape is not perfect but it is very easy to use and generally gives great results. However, sometimes your parts can pull the tape up off the bed during printing, and you will see some warping when that happens.
NOTE: PLA will not stick well to Blue Tape when it is warm. You do not want to heat the bed if you plan to print on Blue Tape. Also, the surface of the Blue Tape will lose its ability to hold onto a part with use. You should replace the tape when you start to see the adhesion degrading (usually somewhere between 5-10 prints on the same spot).
PRINTING ON GLASS WITH A HEATED BED
Printing raftless is best with a sheet of glass, however you must ensure your bed is manually level - check the manual how to do this.
- Having your bed level and extruder at the right height is extremely important when printing on glass. If your extruder is too far from the glass your PLA will not stick AT ALL, if it is too low the glass will completely block the extrusion of material and it will not stick AT ALL.
- If your first layer is not sticking
- Make sure the bed is level.
- Make sure the print head is close enough to make a nice squished first layer.
- Clean the glass with acetone or alcohol
When you can get it working well, glass is the absolute best way to print PLA. It makes for a shiny bottom layer and the heated bed ensures that parts stay nice and flat.